System and method for controlling chiller

Abstract

A heating, ventilation, air conditioning and refrigeration (HVACamp; HVACamp; HVACamp; HVACamp; HVACamp; r) system includes: a mechanical cooling system configured to place a working fluid in a heat exchange relationship with a cooling fluid; a free cooling system configured to place the cooling fluid in a second heat exchange relationship with a flow of ambient air; and a controller including processing circuitry and a memory, where the memory includes instructions that, when executed by the processing circuitry, are configured to cause the processing circuitry to be based on the HVACamp; r is a cooling requirement of the system and is based on the HVACamp; r an estimated power consumption of the system to transition the HVACamp between the plurality of cooling modes; and R, operating the system.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Provisional Application No. 63 / 350,312, filed on June 8, 2022, entitled “SYSTEMS AND METHOD FOR CONTROLLINGA CHILLER,” which is incorporated herein by reference in its entirety for all purposes. Background Art

[0003] This section is intended to introduce the reader to various aspects of the technology that may be related to various aspects of the present disclosure described below. It is believed that this discussion helps to provide the reader with background information to promote a better understanding of various aspects of the present disclosure. Therefore, it should be understood that these statements should be read in this light, rather than as an admission of the prior art.

[0004] A chiller system or vapor compression system utilizes a working fluid (e.g., a refrigerant) that changes phase between vapor, liquid, and combinations thereof in response to exposure to different temperatures and pressures within components of the chiller system. The chiller system may include an evaporator configured to place a working fluid (e.g., a refrigerant) in a heat exchange relationship with a cooling fluid (e.g., water) such that the working fluid absorbs heat from the cooling fluid. The cooling fluid cooled by the working fluid may then be delivered to a conditioning device and / or a conditioned environment served by the chiller system. In such applications, the cooling fluid may be directed through downstream equipment such as an air handler to condition other fluids, such as air within a building.

[0005] In some chiller systems, a conditioning fluid (e.g., air, water) can be used additionally or alternatively to cool a working fluid. For example, a chiller system may include a cooling tower (or other water source or cooling fluid source), which is configured to provide a conditioning fluid to a condenser of a chiller system. The conditioning fluid can be cooled via ambient air in a cooling tower (or other water source or cooling fluid source), and the condenser can place the conditioning fluid from the cooling tower in a heat exchange relationship with the working fluid to transfer heat from the working fluid to the fluid. A compressor can be positioned between the condenser and the evaporator, and can be operated to regulate the pressure of the working fluid and circulate the working fluid between the components of the chiller system.

[0006] In some applications, the chiller can operate in a free cooling mode, which can be activated under certain conditions, such as when the ambient air temperature is relatively low (e.g., in spring, winter, and / or fall). When the ambient air temperature is relatively low, the cooling demand of the chiller system may be reduced and / or the operating conditions may enable the chiller to operate with sufficient cooling capacity without utilizing a compressor. For example, because the cooling fluid has a relatively low temperature when the ambient temperature of the outside air is relatively low, the chiller system can operate with sufficient capacity to cool the cooling fluid without operating the compressor. Unfortunately, it may be difficult to efficiently transition the chiller system between different operating modes. Summary of the invention

[0007] The following describes an overview of certain embodiments disclosed herein. It should be understood that these aspects are presented only to provide the reader with a brief overview of these specific embodiments, and these aspects are not intended to limit the scope of the present disclosure. In fact, the present disclosure may cover various aspects that may not be described below.

[0008] In one embodiment, a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system configured to operate in multiple cooling modes includes: a mechanical cooling system configured to place a working fluid in a heat exchange relationship with a cooling fluid; a free cooling system configured to place the cooling fluid in a second heat exchange relationship with an ambient air flow; and a controller including a processing circuit system and a memory, wherein the memory includes instructions that, when executed by the processing circuit system, are configured to cause the processing circuit system to transition operation of the HVAC&R system between the multiple cooling modes based on a cooling demand of the HVAC&R system and based on an estimated power consumption of the HVAC&R system.

[0009] In another embodiment, a tangible, non-transitory computer-readable medium includes instructions executable by a processing circuit system of a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system, which instructions, when executed by the processing circuit system, cause the processing circuit system to: operate a mechanical cooling system and a free cooling system in a hybrid cooling mode of the HVAC&R system, calculate an estimated total amount of cooling capacity provided by the HVAC&R system in the hybrid cooling mode, and calculate a first estimate of input power consumed by the mechanical cooling system and the free cooling system in the hybrid cooling mode to provide the total amount of cooling capacity. The instructions, when executed, further cause the processing circuit system to: determine a total amount of cooling capacity that operation of the free cooling system and suspended operation of the mechanical cooling system in the free cooling mode of the HVAC&R system is expected to provide, calculate a second estimate of input power consumed by the free cooling system in the free cooling mode to provide the total amount of cooling capacity, compare the first estimate of input power to the second estimate of input power; and transition operation of the HVAC&R system from the hybrid cooling mode to the free cooling mode in response to a determination that the second estimate of input power is less than the first estimate of input power.

[0010] In another embodiment, a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system includes: a mechanical cooling system configured to circulate a working fluid therethrough and transfer heat from the cooling fluid to the working fluid; a free cooling system configured to circulate a cooling fluid therethrough and transfer heat from the cooling fluid to ambient air; and a controller. The controller is configured to: operate the mechanical cooling system in a mechanical cooling mode of the HVAC&R system and suspend operation of the free cooling system, operate the free cooling system in a free cooling mode of the HVAC&R system and suspend operation of the mechanical cooling system, operate the mechanical cooling system and operate the free cooling system in a hybrid cooling mode of the HVAC&R system, and transition operation of the HVAC&R system between the mechanical cooling mode, the free cooling mode, and the hybrid cooling mode based on a cooling demand of the HVAC&R system, a first power consumption associated with operation of the mechanical cooling system, and a second power consumption associated with operation of the free cooling system. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Various aspects of the present disclosure may be better understood after reading the following detailed description and referring to the drawings, in which:

[0012] Figure 1 is a perspective view of an embodiment of a building utilizing a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system in a commercial environment according to an aspect of the present disclosure;

[0013] Figure 2is a perspective view of an embodiment of a vapor compression system according to an aspect of the present disclosure, the vapor compression system may include a free cooling system and a mechanical cooling system;

[0014] Figure 3 is a schematic diagram of an embodiment of a vapor compression system having a mechanical cooling system and a free cooling system according to an aspect of the present disclosure;

[0015] Figure 4 is a schematic diagram of an embodiment of a vapor compression system having a mechanical cooling system and a free cooling system according to an aspect of the present disclosure;

[0016] Figure 5 is a schematic diagram of an embodiment of a vapor compression system having a mechanical cooling system and a free cooling system according to an aspect of the present disclosure;

[0017] Figure 6 is a graphical representation of ambient temperature according to cooling load requirements for various operating modes of a vapor compression system according to an aspect of the present disclosure; and

[0018] Figure 7 is a flow chart of an embodiment of a method for controlling transitions between operating modes of a vapor compression system. DETAILED DESCRIPTION

[0019] The present disclosure of one or more specific embodiments of the present invention will be described below. These described embodiments are examples of the currently disclosed technology. In addition, in the process of striving to provide a concise description of these embodiments, all features of the actual implementation scheme may not be described in the specification. It should be understood that in the development of any such actual implementation scheme, as in any engineering or design project, numerous implementation scheme specific decisions can be made to achieve the specific goals of the developer, such as complying with system-related and business-related constraints, which may vary from one implementation scheme to another. In addition, it should be understood that such development work may be complex and time-consuming, but will be a routine task of design, production and manufacturing for ordinary technicians who benefit from the present disclosure.

[0020] When introducing elements of various embodiments of the present disclosure, the articles "a," "an," and "the" are intended to indicate that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements in addition to the listed elements. Additionally, it should be understood that references to "one embodiment" or "an embodiment" of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that are further incorporated into the recited features.

[0021] As used herein, the terms "approximately," "substantially," "substantially," and the like are intended to convey that the value of the property being described may be within a relatively small range of that property value, as understood by one skilled in the art. For example, when a property value is described as being "approximately" equal to (or, for example, "substantially similar to") a given value, this is intended to convey that the property value may be within + / -5%, within + / -4%, within + / -3%, within + / -2%, within + / -1%, or even closer of the given value. Similarly, when a given feature is described as being "substantially parallel" to another feature, "substantially perpendicular" to another feature, and the like, this is intended to convey that the given feature is within + / -5%, within + / -4%, within + / -3%, within + / -2%, within + / -1%, or even closer of the described property, such as being parallel to another feature, being perpendicular to another feature, and the like. Mathematical terms, such as "parallel" and "perpendicular," should not be strictly interpreted in a strict mathematical sense, but rather should be interpreted as one of ordinary skill in the art would interpret such terms. For example, one of ordinary skill in the art will understand that two lines that are generally parallel to each other are largely parallel, but may have slight deviations from being completely parallel.

[0022] Embodiments of the present disclosure generally relate to a heating, ventilation, air conditioning and refrigeration (HVAC&R) system utilizing a vapor compression system, which HVAC&R system may be referred to herein as a chiller or chiller system. More specifically, embodiments of the present disclosure relate to a control system (e.g., a control scheme) for a chiller system including a free cooling system and a mechanical cooling system. As will be appreciated, a free cooling system may include a system that places a fluid (e.g., a heat transfer fluid, a cooling fluid) in a heat exchange relationship with ambient air. Thus, a free cooling system may utilize ambient air in an ambient environment as a cooling fluid and / or a heating fluid. The HVAC&R system may operate utilizing a free cooling system alone (e.g., a free cooling mode), utilizing a mechanical cooling system alone (e.g., a mechanical cooling mode), or utilizing both a free cooling system and a mechanical cooling system (e.g., a mixed cooling mode). In order to determine which system(s) of the HVAC&R system is to be operated (e.g., an operating mode of operation), the HVAC&R system may include various sensors and / or other monitoring devices that measure operating conditions of the HVAC&R system (e.g., fan speed, compressor speed, ambient air temperature, and conditioning fluid temperature). For example, according to embodiments of the present disclosure, the determination of which system(s) to operate may depend at least on the expected cooling load demand (e.g., expected load temperature) and / or the ambient air temperature (e.g., the temperature of the surrounding environment of the HVAC&R system).

[0023] As described above, the currently disclosed chiller system (e.g., refrigeration system, vapor compression system) can be configured to operate in various operating modes (e.g., various cooling modes) based on certain conditions (e.g., environmental conditions, operating conditions) associated with the chiller system. For example, during the free cooling mode, the chiller system can circulate a cooling fluid (e.g., heat transfer fluid, water, glycol, brine) through a heat exchanger to achieve heat exchange from the cooling fluid to ambient air. In the free cooling mode, a fan can be operated to guide the flow of ambient air across the heat exchanger. During the operation of the chiller system in the free cooling mode, the compressor of the mechanical cooling system may not operate (e.g., may not be powered). During the mechanical cooling mode, the chiller is configured to circulate a working fluid (e.g., a refrigerant) through a mechanical cooling system (e.g., a compressor, an evaporator, a condenser, and an expansion valve, among other possible components) of the chiller system. Therefore, in the mechanical cooling mode, the compressor is powered to circulate the working fluid through the mechanical cooling system. The evaporator can place the working fluid and the cooling fluid (e.g., water) in a heat exchange relationship so that the working fluid absorbs heat from the cooling fluid. The cooling fluid may be circulated between the evaporator and other equipment, such as air handling equipment in a building, where the cooling fluid is used to cool the air flow delivered to the conditioned space. In some embodiments, an air handling unit (AHU) of the HVAC&R system may receive the cooling fluid from the chiller system and use the cooling fluid to cool the air flow delivered to the conditioned space. The cooling fluid may then be returned to the chiller system to be cooled again.

[0024] Under certain conditions, such as during autumn, winter and / or spring, ambient air or other cooling media may be relatively cold. Relatively cold ambient air can enable the chiller system to operate more efficiently to meet cooling needs. For example, in a free cooling mode of operation, the chiller system can guide (e.g., via the operation of a fan) ambient air across a heat exchanger of a free cooling system, and a cooling fluid circulates through the heat exchanger to cool the cooling fluid. Further, relatively cold ambient air can also be used to cool a working fluid of a mechanical cooling system. For example, the chiller system can guide (e.g., via the operation of a fan) ambient air across a heat exchanger (e.g., a condenser) of a mechanical cooling system (e.g., a heat exchanger different from a free cooling system), and a working fluid circulates through the heat exchanger to cool the working fluid. The working fluid can then be directed to the evaporator of the mechanical cooling system to cool the cooling fluid. Therefore, under certain conditions, ambient air can be used to improve the operation of the chiller in free cooling mode and mechanical cooling mode.

[0025] During the hybrid cooling mode, the HVAC&R system may be configured to operate a mechanical cooling system and a free cooling system (e.g., simultaneously). For example, the compressor of the vapor compression system may be operated at a reduced capacity to provide a portion of the total cooling capacity to meet the load demand of the HVAC&R system, and one or more fans of the free cooling system may be operated to provide another portion of the total cooling capacity to meet the load demand of the HVAC&R system. Typically, an HVAC&R system that employs a free cooling system and a mechanical cooling system is configured to operate the free cooling system at an upper capacity limit before operating the mechanical cooling system, because it is generally believed that the free cooling system (e.g., one or more fans of the free cooling system) consumes less power than the mechanical cooling system (e.g., the compressor of the vapor compression cycle). For example, the free cooling system may include one or more fans that direct ambient air across the coils of a heat exchanger to cool the cooling fluid flowing through the coils. In order to operate the fans, power is supplied to the one or more fans to drive the operation of the fans, thereby forcing the ambient air to cross the coils and enabling the ambient air to absorb heat from the cooling fluid. On the other hand, in the mechanical cooling mode, the HVAC&R system consumes power via the operation of the compressor of the mechanical cooling system. Thus, in the hybrid cooling mode described herein, the HVAC&R system may consume power via operation of the fans of the free cooling system and operation of the compressor of the mechanical cooling system.

[0026] In conventional systems configured to operate in multiple modes (e.g., cooling mode, mechanical cooling mode, hybrid cooling mode, free cooling mode), it may be difficult to efficiently transition between different cooling modes and / or efficiently balance the load demands between the free cooling system and the mechanical cooling system in the hybrid operating mode. Therefore, it is now recognized that improved systems and methods are desired for controlling transitions between different cooling modes of a vapor compression system. According to the present technology, certain embodiments include a control system that can be used to more efficiently transition an HVAC&R system between cooling modes so as to increase the efficiency (e.g., energy efficiency) of the HVAC&R system overall. For example, the control system can be configured to estimate energy usage values ​​(e.g., total input power) of the HVAC&R system for different cooling modes based on current operating conditions and / or expected operating conditions. Based on the estimated energy usage values, the control system can determine whether to transition the operation of the HVAC&R system to a different cooling mode (e.g., to meet an existing load demand on the HVAC&R system). For example, the control scheme may be configured to calculate the energy consumption level (e.g., total input power) of the current cooling mode (e.g., mechanical cooling mode, hybrid cooling mode, free cooling mode) and calculate the expected energy consumption levels for different cooling modes (e.g., mechanical cooling mode, hybrid cooling mode, free cooling mode). Based on a comparison of the energy consumption level of the current operating mode and the expected energy consumption levels for the different operating modes, the control system may determine whether to transition the operation of the HVAC&R system to a different operating mode. For example, based on a determination that the different operating mode will result in increased energy efficiency (e.g., the HVAC&R system utilizes less input power to meet the current load demand), the control system may transition the operation to a different operating mode. In this manner, the present embodiment enables the operation of the HVAC&R system to be improved by increasing energy efficiency, thereby reducing costs (e.g., energy costs) associated with the operation of the chiller.

[0027] Turning now to the accompanying drawings, Figure 1 is a perspective view of an embodiment of a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system 10 for a building 12 in a typical commercial environment. The HVAC&R system 10 can provide cooling to a data center, electrical installation, freezer, chiller, or other environment via vapor compression refrigeration, absorption refrigeration, and / or thermoelectric cooling. However, in the presently contemplated applications, the HVAC&R system 10 can also be used in residential, commercial, light industrial, industrial, and any other application for heating or cooling a space or enclosure, such as a residence, building 12, structure, etc. In addition, the HVAC&R system 10 can be used in industrial applications and, where appropriate, for cooling and heating of various fluids.

[0028] In the illustrated embodiment, the building 12 is cooled by a system including an HVAC&R system 10 (e.g., a chiller system, an air-cooled chiller) and a boiler 14. As shown, the HVAC&R system 10 is disposed on the roof of the building 12, and the boiler 14 is located in the basement; however, the HVAC&R system 10 and the boiler 14 may be located in other equipment rooms or areas adjacent to the building 12. The HVAC&R system 10 is an air-cooled device and / or a mechanical cooling system that implements a refrigeration cycle to cool a cooling fluid, such as water, glycol, or other heat transfer fluid. The HVAC&R system 10 is received within a structure that includes a mechanical cooling system, a free cooling system, and associated equipment such as pumps, valves, and piping. For example, the HVAC&R system 10 may be a single, integrated rooftop unit that incorporates a free cooling system and a mechanical cooling system. The boiler 14 is a closed container that includes a furnace for heating a heating fluid. The cooling fluid from the HVAC&R system 10 and the heating fluid from the boiler 14 are circulated through the building 12 via a conduit 16. Ducts 16 are routed to air handlers 18 located on individual floors and within portions of building 12 .

[0029] The air handler 18 is coupled to a duct system 20 that is adapted to distribute air between the air handlers 18 and may receive air from an external inlet. The air handler 18 includes a heat exchanger that circulates cold cooling fluid from the HVAC&R system 10 and hot heating fluid from the boiler 14 to provide heated or cooled air. A fan within the air handler 18 draws air across the coils of the heat exchanger and directs the conditioned air to an environment such as a room, apartment, or office within the building 12 to maintain the environment at a specified temperature. The control device shown as including a thermostat 22 can be used to specify the temperature of the conditioned air. The control device 22 can also be used to control the flow of air through and from the air handler 18. Of course, other devices may be included in the system, such as control valves that regulate the flow and pressure of cooling fluid / heating fluid and / or temperature sensors or switches that sense the temperature and pressure of cooling fluid / heating fluid, air, etc. In addition, the control device 22 may include a computer system that is integrated with and / or separate from other building control or monitoring systems (including systems remote from the building 12).

[0030] According to an embodiment of the present disclosure, the HVAC&R system 10 may include a mechanical cooling system and a free cooling system. For example, Figure 2is a perspective view of an embodiment of an HVAC&R system 10 that may include a mechanical cooling system (e.g., a vapor compression refrigeration cycle) and a free cooling system configured to improve the efficiency of the HVAC&R system 10. The free cooling system and the mechanical cooling system may operate alone or in combination with each other. In certain embodiments, the HVAC&R system 10 may include a control system configured to determine whether and how to operate the mechanical cooling system and / or the free cooling system based on various operating parameters of the HVAC&R system 10, such as the temperature of ambient air (e.g., air in the surrounding environment of the HVAC&R system 10) and / or a cooling load demand (e.g., the amount of cooling required by the load). The HVAC&R system 10 may operate the mechanical cooling system alone (e.g., in a mechanical cooling mode), operate the free cooling system alone (e.g., in a cooling mode), or operate the mechanical cooling system and the free cooling system in combination with each other (e.g., a hybrid cooling mode) to meet the cooling load demand.

[0031] As described above, it may be desirable to limit or reduce the amount of energy input to the HVAC&R system 10 in order to improve the efficiency of the HVAC&R system 10. In a typical system, before the compressor of the mechanical cooling system is started (e.g., initialized, operated), the speed of the fan of the free cooling system may be increased to an upper limit or capacity in order to achieve the desired cooling load. However, it is now recognized that improved transitions between one or more available operating modes (e.g., free cooling mode, hybrid cooling mode, mechanical cooling mode) can enable the HVAC&R system 10 to meet load demands while limiting the amount of energy consumed, thereby increasing the efficiency of the HVAC&R system 10. Therefore, the present disclosure is directed to a control system for the HVAC&R system 10 that is configured to control transitions between operating modes of the HVAC&R system 10 and enable the mechanical cooling system and the free cooling system to operate more efficiently.

[0032] For example, Figure 3is a block diagram of an embodiment of an HVAC&R system 10 that may be utilized in accordance with the present technology. As shown in the illustrated embodiment, the HVAC&R system 10 includes a free cooling system 52 and a mechanical cooling system 54 (e.g., one or more vapor compression systems). The free cooling system 52 may include an air-cooled heat exchanger 56 (e.g., a free cooling heat exchanger, a free cooling coil) that may receive and cool a cooling fluid 58 (e.g., water, glycol, brine, a heat transfer fluid). For example, the air-cooled heat exchanger 56 may be positioned along an air flow path 59 formed by one or more fans 60 that direct air (e.g., ambient air) over one or more coils of the air-cooled heat exchanger 56. One or more of the fans 60 may be coupled to a variable speed drive (VSD) 61 that may receive alternating current (AC) power having a specific fixed line voltage and a fixed line frequency from an AC power source and provide power having a variable voltage and frequency to a corresponding fan 60 coupled to the VSD 61. In this manner, the speed of one or more fans 60 may be controlled (e.g., adjusted) so that the amount of cooling capacity provided by the free cooling system 52 can be adjusted. The air-cooled heat exchanger 56 may include a round tube plate fin coil with internal reinforcement tubes and louvered fins to improve heat transfer. When the ambient air is at a relatively low temperature, the air directed across the coil of the air-cooled heat exchanger 56 may absorb heat from the cooling fluid 58, thereby reducing the temperature of the cooling fluid 58 and increasing the temperature of the ambient air flowing across the coil of the air-cooled heat exchanger 56. In certain embodiments, the cooling fluid 58 may be received by the air-cooled heat exchanger 56 from a load 62. Thus, the cooling fluid 58 may ultimately be redirected toward the load 62 to reduce the temperature of the load 62 (e.g., air or fluid that may be directed through a building or machine).

[0033] However, the free cooling system 52 may not be as effective or efficient under certain operating conditions, such as when the temperature of the ambient air is relatively high. For example, as the temperature of the ambient air increases, the amount of heat transferred between the cooling fluid 58 and the ambient air in the air-cooled heat exchanger 56 may decrease (e.g., when the ambient air is relatively warm, the ambient air may not absorb as much heat from the cooling fluid 58). Therefore, the HVAC&R system 10 may include a valve 64 (e.g., a three-way valve, a regulating valve, an electronically controlled valve [ECV]) that controls the amount of cooling fluid 58 that can flow toward the free cooling system 52. For example, when the ambient air temperature is sufficiently lower than the temperature of the cooling fluid 58 returning from the load 62, the valve 64 may prevent the cooling fluid 58 from flowing directly from the load 62 toward the evaporator 66 of the mechanical cooling system 54, and at the same time enable the cooling fluid 58 to flow through the air-cooled heat exchanger 56, so that free cooling supplies at least a portion of the cooling load demand. In some cases, such as during operation of the HVAC&R system 10 in the hybrid cooling mode, the cooling fluid 58 may then flow through the evaporator 66 , which may further cool the cooling fluid 58 .

[0034] like Figure 3 As shown in the illustrated embodiment of , valve 64 can receive cooling fluid 58 from pump 65 and can be selectively operated to direct the flow of cooling fluid 58 toward evaporator 66 (e.g., directly from load 62), toward air-cooled heat exchanger 56, then toward evaporator 66, or both. In certain embodiments, valve 64 can be a three-way valve that includes a three-way and two two-way butterfly valves that are mechanically coupled to an actuator that can adjust the position of the valve (e.g., one butterfly valve is open and the other butterfly valve is closed). It should be noted that although in Figure 3 In the embodiment of the present invention, the valve 64 is positioned upstream of the air-cooled heat exchanger 56 (e.g., relative to the flow of the cooling fluid 58), but in other embodiments, the valve 64 can be positioned downstream of the air-cooled heat exchanger 56. In still further embodiments, the valve 64 can be a regulating valve configured to simultaneously supply and control the flow of the cooling fluid 58 from the load 62 to the air-cooled heat exchanger 56 and the evaporator 66, respectively.

[0035] During operating conditions where free cooling can provide substantially all of the cooling load demand (e.g., when the ambient air temperature is below a threshold temperature), the mechanical cooling system 54 may not operate, such that the HVAC&R system 10 operates in a free cooling mode. In the free cooling mode, the valve 64 may be controlled to direct all or substantially all of the cooling fluid 58 from the load 62 through the air-cooled heat exchanger 56. In some embodiments, the cooling fluid 58 may then be directed to flow through the evaporator 66. When operation of the mechanical cooling system 54 is suspended in the free cooling mode, the cooling fluid 58 may flow through the evaporator 66 without experiencing a significant temperature change (e.g., substantially no heat may be transferred from the cooling fluid 58 in the evaporator 66). In some embodiments, the HVAC&R system 10 may include a bypass valve 67 to enable the flow of the cooling fluid 58 (or a portion of the cooling fluid 58) to bypass the evaporator 66. In certain embodiments, controlling the flow of the cooling fluid 58 to bypass the evaporator 66 may substantially avoid a pressure drop experienced by the cooling fluid 58 that may otherwise be caused by flowing through the evaporator 66.

[0036] During operating conditions where free cooling is unable to provide substantially all of the cooling load demand, the mechanical cooling system 54 may be operated (e.g., alone or simultaneously with the free cooling system 52). In certain embodiments, the mechanical cooling system 54 may be a vapor compression system 68 that includes an evaporator 66, a compressor 70, a condenser 72, and / or an expansion device (e.g., an expansion valve) 74, among other components. For example, the mechanical cooling system 54 may be configured to circulate a working fluid 76 (e.g., a refrigerant) that may evaporate (e.g., vaporize) in the evaporator 66 via heat transfer with the cooling fluid 58 (e.g., the cooling fluid 58 transfers thermal energy to the working fluid 76 in the evaporator 66). Thus, heat may be transferred from the cooling fluid 58 to the working fluid 76 within the evaporator 66, thereby reducing the temperature of the cooling fluid 58 (e.g., in place of or in addition to the free cooling system 52). In certain embodiments, the cooling fluid 58 and / or the working fluid 76 may include ethylene glycol, a mixture of ethylene glycol and water, brine, or another suitable fluid. In some embodiments, the working fluid 76 can be any suitable refrigerant, such as a hydrofluorocarbon (HFC) based refrigerant, for example, R-410A, R-407, R-134a, R-1234ze, R1233zd, a hydrofluoroolefin (HFO), a "natural" refrigerant such as ammonia (NH3), R-717, carbon dioxide (CO2), R-744, or a hydrocarbon based refrigerant, or any other suitable refrigerant.

[0037] The evaporator 66 may be a brazed plate, a direct expansion (DX) shell and tube heat exchanger, a flooded shell and tube heat exchanger, a falling film shell and tube heat exchanger, a hybrid falling film and flooded heat exchanger, another type of heat exchanger, or any combination thereof. For embodiments utilizing a direct expansion (DX) evaporator, the working fluid (e.g., refrigerant) 76 may flow on the tube side of the evaporator 66, and the cooling fluid 58 may flow through the evaporator 66 along one or more channels (e.g., two, three, four, or more channels). For embodiments utilizing an evaporator with the refrigerant on the shell side of the evaporator 66, the cooling fluid 58 may flow through the tubes within the shell of the evaporator 66 in one, two, three, or more channels.

[0038] The working fluid (e.g., refrigerant) 76 exiting the evaporator 66 may flow toward the compressor 70, which is configured to circulate the working fluid 76 through the vapor compression system 68. In addition, the compressor 70 may increase the pressure of the working fluid 76 as the working fluid 76 circulates (e.g., periodically circulates) through the vapor compression system 68. Increasing the pressure of the working fluid 76 may also increase the temperature of the working fluid 76, such that the temperature of the working fluid 76 exiting the compressor 70 is greater than the temperature of the working fluid 76 entering the compressor 70. Therefore, it may be desirable to reduce the temperature of the working fluid 76 so that the working fluid 76 may ultimately absorb heat from the cooling fluid 58 in the evaporator 66. In some embodiments, the compressor 70 may be driven by a motor 69, which may be powered by a variable speed drive (VSD) 71. The VSD 71 receives alternating current (AC) power having a specific fixed line voltage and a fixed line frequency from an AC power source, and provides the specific fixed line voltage, fixed line frequency to the motor 69 to drive the compressor 70.

[0039] The working fluid 76 exiting the compressor 70 may flow toward the condenser 72. In certain embodiments, the condenser 72 of the mechanical cooling system 54 may be an air-cooled heat exchanger, similar to the air-cooled heat exchanger 56 of the free cooling system 52. In some embodiments, one or more sets of coils of the condenser 72 may include microchannel coils configured to circulate the working fluid 76 therethrough. In embodiments of the condenser 72 configured as an air-cooled heat exchanger, the condenser 72 may share a fan 60 with the air-cooled heat exchanger 56. In other embodiments, separate fans may direct separate air flows across the air-cooled heat exchanger 56 and the condenser 72. Figure 3As shown in the illustrated embodiment of FIG. 5 , the condenser 72 can be positioned downstream of the air-cooled heat exchanger 56 with respect to the air flow path 59. Thus, ambient air can first be directed across the air-cooled heat exchanger 56 of the free cooling system 52 and can then flow across the condenser 72. In this way, free cooling of the cooling fluid 58 can be improved. In other embodiments, the condenser 72 can include a fan 77 separate from the fan 60 (e.g., see FIG. 5 ). Figure 4 and 5 ). In yet further embodiments, the condenser 72 of the mechanical cooling system 54 can be any suitable heat exchanger configured to transfer heat from the working fluid 76 to another medium (e.g., water, air). In any case, the condenser 72 is configured to reduce the temperature of the working fluid 76 and generally liquefy (e.g., condense) the working fluid 76.

[0040] In certain embodiments, the mechanical cooling system 54 may also include an expansion device 74, which may further reduce the temperature of the working fluid 76, as well as reduce the pressure of the working fluid 76. The expansion device 74 may include an expansion valve, a flash tank, an expansion coil, another device configured to reduce the pressure of the working fluid 76 (and reduce the temperature of the working fluid 76), or any combination thereof. In other embodiments, the mechanical cooling system 54 may not utilize an expansion device 74.

[0041] As described above, the cooling fluid 58 may be reduced in temperature by flowing through the free cooling system 52 and / or the evaporator 66 of the mechanical cooling system 54. However, when the cooling load demand (e.g., a predetermined and / or desired temperature of the load 62 and / or a predetermined temperature of the cooling fluid 58 leaving the evaporator 66) exceeds the capacity of the free cooling system 52 alone, the free cooling system 52 and the mechanical cooling system 54 may be operated in conjunction with one another (e.g., simultaneously in a hybrid cooling mode). Thus, the cooling fluid 58 may be directed toward the air-cooled heat exchanger 56 of the free cooling system 52, whereby the temperature of the cooling fluid 58 may be reduced from a first temperature to a second temperature (e.g., the second temperature is less than the first temperature). Additionally, in the hybrid cooling mode, the cooling fluid 58 may be directed toward the evaporator 66 of the mechanical cooling system 54 upon exiting the air-cooled heat exchanger 56. During operation of the HVAC&R system 10 in the hybrid cooling mode, upon entering the evaporator 66, the temperature of the cooling fluid 58 may be further reduced from the second temperature to a third temperature (e.g., the third temperature is less than the second temperature, and therefore less than the first temperature). Upon exiting the evaporator 66 , the cooling fluid 58 may be directed toward the load 62 , and the cooling fluid 58 may be used to cool the load 62 .

[0042] In certain operations, a first portion of the cooling fluid 58 may be directed from the load 62 toward the air-cooled heat exchanger 56 of the free cooling system 52, while a second portion of the cooling fluid 58 may be directed from the load 62 toward the evaporator 66 of the mechanical cooling system 54 (e.g., via valve 64). In other operations, generally all of the cooling fluid 58 may flow through the air-cooled heat exchanger 56 before entering the evaporator 66 or may flow directly through the evaporator 66.

[0043] HVAC&R system 10 may include a controller 78 (e.g., a control system, an automation controller) that may adjust the position of valve 64, the position of bypass valve 67, the speed of one or more fans 60 (e.g., via VSD 61), the speed of one or more fans 77 (e.g., see Figure 5 ), the speed of the compressor 70 (e.g., via the VSD 71), and / or any other operating parameter of the HVAC&R system 10 that may affect the temperature of the cooling fluid 58 supplied to the load 62. The controller 78 may regulate the operation of the HVAC&R system 10 and its components based on data or feedback provided to the controller 78. Thus, the HVAC&R system 10 may include one or more sensors that may monitor the operating conditions of the HVAC&R system 10. For example, the HVAC&R system 10 may include a return cooling fluid temperature sensor 81, a supply cooling fluid temperature sensor 83, a suction pressure and / or temperature sensor 85, a discharge pressure and / or temperature sensor 87, and / or an ambient temperature and / or pressure sensor 89. The temperature and / or pressure sensors may provide feedback to the controller 78, which may then adjust the position of the valve 64, the position of the bypass valve 67, the speed of the one or more fans 60 (e.g., via the VSD 61), the one or more fans 77 ( Figure 5 ) speed and / or the speed of compressor 70 (e.g., via VSD 71).

[0044] In certain embodiments, the controller 78 may include a processing circuit system 80 (e.g., one or more microprocessors) and a memory 82. The processing circuit system 80 may include multiple microprocessors, one or more "general purpose" microprocessors, one or more special purpose microprocessors, and / or one or more application specific integrated circuits (ASICs), or some combination thereof. For example, the processing circuit system 80 may include one or more reduced instruction set (RISC) processors. The controller 78 may include non-transitory code or instructions stored on a machine-readable medium (e.g., memory 82) that are executed by the processing circuit system 80 to implement the techniques disclosed herein. The memory 82 may include volatile memory (such as random access memory (RAM)) and / or non-volatile memory (such as read-only memory (ROM), an optical drive, a hard drive, a solid-state drive, or any other non-transitory computer-readable medium storing instructions that, when executed by the processing circuit system 80, control the operation of the HVAC&R system 10. In addition, the memory 82 may store experimental data and / or other values ​​related to predetermined operating conditions of the HVAC&R system 10. The controller 78 can monitor and control the operation of the HVAC&R system 10, for example, by adjusting the position of the valve 64, the position of the bypass valve 67, the speed of one or more fans 60, the speed of one or more fans 77, and / or the speed of the compressor 70 based on feedback received from one or more sensors. In practice, in accordance with the present technology, the controller 78 can be configured to control the HVAC&R system 10 to transition between one or more operating modes described herein. Further, the controller 78 can be configured to balance the cooling load or load demand of the HVAC&R system 10 between the free cooling system 52 and the mechanical cooling system 54. In this way, the controller 78 of the HVAC&R system 10 can be configured to perform operations that can improve the efficiency of the HVAC&R system 10. Reference will be made herein to Figure 7 Such operations are discussed in more detail.

[0045] Figure 4is a block diagram of an embodiment of the HVAC&R system 10, showing a mechanical cooling system 54 having a vapor compression system 68 (e.g., a first vapor compression system) and a second vapor compression system 90. The second vapor compression system 90 may include a second compressor 91, a second condenser 92, and a second expansion device 93. In addition, the second vapor compression system 90 may be configured to direct a working fluid (e.g., a refrigerant) 94 through the evaporator 66 to provide additional cooling when the cooling load demand is relatively high. The second vapor compression system 90 may be configured to operate in substantially the same manner as the vapor compression system 68 described above to provide a cooled working fluid 94 to the evaporator 66 so that the cooled working fluid 94 can absorb heat from the cooling fluid 58. In some embodiments, the working fluid 94 may be the same fluid as the working fluid 76 (e.g., water, ethylene glycol, a mixture of water and ethylene glycol, a refrigerant). In other embodiments, the working fluid 94 may be different from the working fluid 76. Further, in some embodiments, the second compressor 91 may also be driven by a motor 86 coupled to a variable speed drive (VSD) 88 , thereby enabling the speed of the second compressor 91 to be controlled to adjust the cooling capacity provided by the second vapor compression system 90 .

[0046] like Figure 4 As shown, the vapor compression systems 68 and 90 share the evaporator 66 (e.g., a single evaporator, a common evaporator). In other words, the evaporator 66 is a component of each of the vapor compression systems 68 and 90. The evaporator 66 can be a shell and tube heat exchanger, in which the working fluids 76 and 94 are located on the shell side of the evaporator 66 and the cooling fluid 58 is located on the tube side of the evaporator. The partition 95 of the evaporator 66 can separate the working fluid flow paths through the evaporator 66 of the two vapor compression systems 68 and 90. In some embodiments, the partition 95 can be used as a tube sheet to support the tubes within the evaporator 66. In other embodiments, when multiple vapor compression systems 68 and 90 are included in the HVAC&R system 10, DX evaporators or brazed plate evaporators can be utilized, and each of the vapor compression systems 68 and 90 incorporated into the HVAC&R system 10 can have a corresponding evaporator.

[0047] like Figure 4As shown in the illustrated embodiment of FIG. 5 , the second condenser 92 may be positioned in an air flow path 96 separate from the condenser 72. In some embodiments, the free cooling system 52 may include a second air-cooled heat exchanger 97 positioned along the air flow path 96, which may share a fan 98 with the second condenser 92. In the illustrated embodiment, air flow (e.g., ambient air) is directed from the ambient environment along the air flow path 59, across the air-cooled heat exchanger 56, across the condenser 72, through the fan 60, and then exhausted from the HVAC&R system 10. Likewise, air flow (e.g., ambient air) is directed from the ambient environment along the air flow path 96, across the second air-cooled heat exchanger 97, across the second condenser 92, through the fan 98, and then exhausted from the HVAC&R system 10. In other embodiments, the condenser 72, the second condenser 92, the air-cooled heat exchanger 56, and / or the second air-cooled heat exchanger 97 may be positioned in any suitable arrangement to meet the cooling load requirements. In yet further embodiments, one or more of the condenser 72, the second condenser 92, the air-cooled heat exchanger 56, and the second air-cooled heat exchanger 97 can share a fan (e.g., the condenser 72, the second condenser 92, the air-cooled heat exchanger 56 and / or the second air-cooled heat exchanger 97 are positioned in the same air flow path) so that, for example, ambient air flows across the air-cooled heat exchanger 56, the second air-cooled heat exchanger 97, the condenser 72, the second condenser 92 and / or the fan 60 in a series flow configuration.

[0048] Additionally, the controller 78 may be communicatively coupled to a second suction pressure and / or temperature sensor 99 and a second discharge pressure and / or temperature sensor 100 to respectively monitor the pressure and / or temperature of the working fluid 94 entering and exiting the second compressor 91. In some embodiments, the pressure and / or temperature of the working fluid 94 entering and exiting the second compressor 91 may enable the controller 78 to determine whether to increase and / or decrease the speed of the second compressor 91 (e.g., via the VSD 88).

[0049] Figure 51 is a block diagram of an embodiment of an HVAC&R system 10 that includes additional components that may be incorporated into the HVAC&R system 10. Specifically, the HVAC&R system 10 includes an economizer 101, a filter 102, an oil separator 104, and / or additional valves that may provide enhanced control of the HVAC&R system 10 to cool the load 62 and thereby enhance the efficiency of the HVAC&R system 10. The economizer 101 is a component of the vapor compression system 68. The economizer 101 may include an expansion device 74 and a flash tank 106. In certain embodiments, the flash tank 106 may receive the working fluid 76 from the expansion device 74 at a relatively low pressure and low temperature. The flash tank 106 may be a container configured to quickly reduce the pressure of the working fluid 76 and even further separate the vapor working fluid from the liquid working fluid. Thus, a first portion of the working fluid 76 may evaporate (e.g., change from liquid to vapor) due to the rapid expansion within the flash tank 106. In some embodiments, a first portion of the vaporized working fluid 76 may bypass the evaporator 66 and be directed toward the compressor 70 via the bypass loop 107. Additionally, a second portion of the working fluid 76 may remain in liquid form and may collect at the bottom 108 of the flash tank 106. In some embodiments, a valve 110 may be included downstream of the flash tank 106 and upstream of the evaporator 66 such that the flow of the second portion of the working fluid 76 (e.g., from the flash tank 106 to the evaporator 66) may be adjusted based on operating parameters of the HVAC&R system 10. For example, when the condenser 72 reduces the temperature of the working fluid 76 to a level such that the first portion exiting the flash tank 106 is substantially less than the second portion, the valve 110 may be adjusted to increase the flow of the second portion of the working fluid 76 directed toward the evaporator 66 such that more of the working fluid 76 is evaporated in the evaporator 66 and directed toward the compressor 70.

[0050] In addition, the flash tank 106 may include a level sensor 111 that can monitor the amount of the second portion (e.g., liquid portion) of the working fluid 76 collected in the bottom 108 of the flash tank 106. The level sensor 111 can be communicatively coupled to the controller 78 to provide feedback to the controller 78 regarding the amount of liquid working fluid collected in the flash tank 106. In certain embodiments, the controller 78 can be configured to perform an output, function, or command based on the feedback received from the level sensor 111. For example, in certain embodiments, the three-way valve 112 can be positioned between the condenser 72 and the economizer 101. In response to a determination that the working fluid level detected in the flash tank 106 reaches or exceeds a threshold level, the three-way valve 112 can be adjusted (e.g., via the controller 78) to direct the working fluid 76 toward the evaporator 66 along the bypass loop 113, thereby bypassing the economizer 101 (e.g., the temperature of the working fluid is too low, and therefore the additional cooling provided by the economizer 101 may not be desired). In addition, in response to a determination that the working fluid level detected in the flash tank 106 has dropped below a predetermined level, the three-way valve 112 can be adjusted (e.g., via the controller 78) so that all or a substantial portion of the working fluid 76 causes additional cooling in the economizer 101 by preventing the flow of the working fluid 76 through the bypass loop 113.

[0051] like Figure 5 As shown in the illustrated embodiment of , the vapor compression system 68 may also include a check valve 115 disposed along the bypass loop 107, which may prevent the first portion of the working fluid 76 from flowing from the compressor 70 toward the flash tank 106. Thus, the first portion of the working fluid 76 (e.g., vapor working fluid) may be directed from the flash tank 106 toward the compressor 70, wherein the pressure of the first portion of the working fluid 76 may be increased. Additionally or alternatively, a valve 116 (e.g., a solenoid valve, a regulating valve) may be disposed along the bypass loop 107 between the flash tank 106 and the compressor 70. The controller 78 may be communicatively coupled to the valve 116, and the controller 78 may adjust the position of the valve 116 (e.g., via an actuator configured to adjust the position of the valve 116) to control the flow of the first portion of the working fluid 76 directed to the compressor 70. It may be desirable to control the flow of the first portion of the working fluid 76 from the flash tank 106 toward the compressor 70, for example, based on the current operating speed or operating capacity of the compressor 70. In some embodiments, in response to a determination that compressor 70 is operating near a predetermined capacity (e.g., an upper capacity limit), controller 78 may adjust valve 116 to reduce the flow rate of the first portion of working fluid 76 flowing toward compressor 70. Similarly, in response to a determination that compressor 70 is generally operating below a predetermined or desired capacity, controller 78 may adjust valve 116 to increase the flow of the first portion of working fluid 76 flowing toward compressor 70.

[0052] Additionally, the vapor compression system 68 may include a filter 102 that may be used to remove contaminants from the working fluid 76. In certain embodiments, acids and / or oils may mix with the working fluid 76 that circulates through the vapor compression system 68. Thus, the filter 102 may be configured to remove contaminants from the working fluid 76 such that the working fluid 76 entering the expansion device 74, the flash tank 106, the compressor 70, and / or the evaporator 66 includes fewer contaminants.

[0053] The vapor compression system 68 may also include an oil separator 104, which may be positioned, for example, downstream of the compressor 70 and upstream of the condenser 72. The oil separator 104 may be used to remove oil that may be entrained in the working fluid 76 flowing through the compressor 70. Therefore, the oil collected by the oil separator 104 may be returned to the compressor 70 from the oil separator 104 via a recirculation loop 117. For example, a valve 118 may be positioned along the recirculation loop 117 to control the flow and / or pressure of the oil returning from the oil separator 104 and flowing toward the compressor 70. The valve 118 may be communicatively coupled to the controller 78. Therefore, the amount of oil returned to the compressor 70 may be regulated by the controller 78 (e.g., via an actuator configured to adjust the position of the valve 118). In certain embodiments, the oil separator 104 may be a flash tank, a membrane separator, or any other device configured to separate oil from the working fluid 76.

[0054] Additionally, a valve 119 may be positioned between the compressor 70 and the oil separator 104 to control the amount of the working fluid 76 that flows toward the oil separator 104. In some cases, the oil separator 104 may include an oil level monitoring device (e.g., an oil level sensor 120) that may enable the controller 78 and / or an operator to determine the amount of oil collected in the oil separator 104. In response to a determination that the amount of oil in the oil separator 104 exceeds a predetermined threshold level, the controller 78 may adjust the position of the valve 119 to reduce the flow of the working fluid 76 toward the oil separator 104. In some embodiments, the controller 78 may also adjust the position of the valve 118 to increase the amount of oil returned from the oil separator 104 to the compressor 70. As a result, the level of oil in the oil separator 104 may be reduced, thereby enabling more of the working fluid 76 to flow toward the oil separator 104, and therefore toward the condenser 72. Although the present discussion focuses on the vapor compression system 68, it should be noted that the second vapor compression system 90 may also include an economizer, a filter, an oil separator, and / or a reference Figure 5 Additional Valves and Components Discussed.

[0055] Figure 61 is a graphical representation 150 of cooling load demand as a function of ambient air temperature in various operating modes of the HVAC&R system 10. The graphical representation assumes a constant temperature of the cooling fluid 58 returning from the load 62 (e.g., the temperature detected by the return cooling fluid temperature sensor 81) and a constant flow rate of the cooling fluid 58. Thus, the graphical illustration 150 illustrates different modes in which the HVAC&R system 10 may operate based at least on the ambient air temperature and the cooling load demand. It should be appreciated that the modes described below may be implemented via operation of the controller 78 described above (e.g., in response to feedback from one or more sensors received by the controller 78).

[0056] like Figure 6 As shown in the illustrated embodiment of the HVAC&R system 10, in response to a determination that the ambient air temperature (e.g., detected by the ambient temperature sensor 89) is below a first threshold temperature line 152 at a particular cooling load demand, the free cooling system 52 can be operated. In other words, the first threshold temperature line 152 can represent an ambient air temperature at which free cooling can effectively and / or efficiently absorb heat from the cooling fluid 58 at different cooling load demands. In some applications, the first threshold temperature line 152 can be determined or established based on the return cooling fluid 58 temperature (e.g., the temperature of the cooling fluid 58 returned from the load 62), the cooling load demand 62, and / or other operating parameters of the HVAC&R system 10. Further, in response to a determination that the ambient air temperature is below a second threshold temperature line 154 at a particular cooling load demand, the HVAC&R system 10 can be operated in a free cooling only mode 156 (e.g., without operating the mechanical cooling system 54). Thus, the second threshold temperature line 154 may represent an ambient air temperature at which the HVAC&R system 10 may meet cooling load demands without utilizing the mechanical cooling system 54 and / or without operating the one or more fans 60 at speeds above a threshold at different cooling load demands. Thus, the ambient temperature represented by the second threshold temperature line 154 may be less than the ambient temperature represented by the first threshold temperature line 152.

[0057] In response to a determination that the ambient air temperature exceeds the second threshold temperature line 154 but is below the first threshold temperature line 152 for a particular cooling load demand, the controller 78 may be configured to operate the compressor 70 of the vapor compression system 68 (e.g., the mechanical cooling system 54) in a first hybrid cooling mode 158. In the first hybrid cooling mode 158, the free cooling system 52 and the vapor compression system 68 (e.g., the mechanical cooling system 54) operate in cooperation to meet the cooling load demand. However, in some cases, under a particular cooling load demand, the ambient air temperature may be below the first threshold temperature line 152, but the free cooling system 52 and the vapor compression system 68 may not be able to fully meet the cooling load demand (e.g., when the cooling load demand exceeds the cooling load demand threshold line 159 for the particular ambient air temperature). Therefore, in addition to the air-cooled heat exchanger 56 (e.g., the free cooling system 52) and the compressor 70 of the vapor compression system 68, the second compressor 91 of the second vapor compression system 90 (e.g., the mechanical cooling system 54) may also be operated to achieve the desired cooling level. In this case, the HVAC&R system 10 may operate in the second hybrid cooling mode 160 .

[0058] When the ambient air temperature increases above the first threshold temperature line 152 for a particular cooling load demand, the free cooling system 52 may consume energy without providing a correspondingly sufficient amount of cooling to meet the particular cooling load demand. In other words, the free cooling system 52 may not operate as efficiently as desired. Therefore, the power supplied to the one or more fans 60 may be suspended and / or blocked, and a first mechanical cooling mode 162 may be implemented. In the first mechanical cooling mode 162, the controller 78 may operate the compressor 70 of the vapor compression system 68 to cool the cooling fluid 58 flowing through the evaporator 66. The first mechanical cooling mode 162 may be used to achieve a desired cooling level below the second cooling load demand threshold line 164 for the corresponding ambient air temperature. Therefore, when the cooling load demand exceeds the second cooling load demand threshold line 164 and the ambient air temperature exceeds the first threshold temperature line 152, the controller 78 may initiate a second mechanical cooling mode 166. In the second mechanical cooling mode 166, the controller 78 may operate both the compressor 70 of the vapor compression system 68 and the second compressor 91 of the second vapor compression system 90 to meet the cooling load demand.

[0059] In certain embodiments, the first threshold temperature line 152 and the second threshold temperature line 154 may intersect at a point 168 along an axis 170 representing ambient air temperature. Point 168 may be less than a point 172 representing the temperature of the cooling fluid 58 returned from the load 62 such that heat may be transferred from the cooling fluid 58 to the ambient air.

[0060] In order to improve the efficiency of the HVAC&R system 10 (e.g., reduce cycling between different operating modes, reduce power consumption), it may be desirable to transition between various cooling modes (e.g., the first mechanical cooling mode 162 and the second mechanical cooling mode 166, the first hybrid cooling mode 158 and the second hybrid cooling mode 160, the free cooling mode 156) employed by the HVAC&R system 10 to meet the load demand of the HVAC&R system 10. In some cases, transitioning from one of the available cooling modes to a different cooling mode may enhance the efficiency of the HVAC&R system 10 by reducing the total input power consumed by the HVAC&R system 10 to meet the load demand. In other words, although two different operating modes (e.g., different cooling modes) may be utilized to meet the load demand, the operation of the HVAC&R system 10 in one of the operating modes may consume less power than the operation in another of the operating modes. Therefore, it is desirable to determine (e.g., estimate) the power consumption of the HVAC&R system 10 in one or more of the possible (e.g., candidate) operating modes to evaluate which operating mode may consume less power while still meeting load demands.

[0061] Figure 7 An embodiment of a method 200 (e.g., transition control scheme, control logic) is shown that can be used to determine whether the operation of the HVAC&R system 10 should be transitioned from one cooling mode to another cooling mode. Specifically, the method 200 can be implemented to enable the power consumption of the HVAC&R system 10 to be reduced while meeting the load demand (e.g., cooling load demand, load 62), and thereby improve the efficiency of the HVAC&R system 10. For example, the controller 78 (e.g., control system, processing circuit system 80) can be configured to implement and / or execute the method 200 to control various components of the HVAC&R system 10 (e.g., transition between different cooling modes). That is, computer executable instructions can be stored on the memory 82, and the processing circuit system 80 can execute the instructions to perform some or all of the steps of the method 200 described below. In other embodiments, the method 200 can be implemented by another controller (e.g., a dedicated controller of the HVAC&R system 10, a vapor compression system controller), more than one controller, or other suitable control system. It should also be noted that additional steps can be performed with respect to the method 200. Additionally, certain steps of the depicted method 20 may be removed, modified, and / or performed in a different order.

[0062] As described above, method 200 may be implemented to determine whether to transition the operation of HVAC&R system 10 from one cooling mode to another cooling mode (e.g., from a mechanical cooling mode to a hybrid cooling mode, from a hybrid cooling mode to a free cooling mode, from one hybrid cooling mode to another hybrid cooling mode) to reduce the total amount of energy consumed by HVAC&R system 10 while still meeting the cooling load (e.g., load 62), thereby improving the efficiency of HVAC&R system 10. Although method 200 is illustrated as a series of steps, it should be understood that method 200 may be performed or implemented as a continuous or continuous control loop based on any suitable input, data, or feedback (e.g., feedback from one or more sensors). That is, the steps of method 200 may be repeatedly performed (e.g., in a continuous order) to enable evaluation of different candidate cooling modes and determine whether it is desirable to transition from one cooling mode to another cooling mode. In practice, method 200 may be performed continuously or continually to dynamically control components of HVAC&R system 10 in real time (e.g., based on feedback provided by one or more sensors) to meet load demands while limiting or reducing energy consumption (e.g., limiting the total power consumed by HVAC&R system 10 to meet load demands). In some embodiments, one or more steps of method 200 may be performed or performed simultaneously.

[0063] In the illustrated embodiment, the method 200 begins with the HVAC&R system 10 operating in a mechanical cooling mode (e.g., operating the mechanical cooling system 54 alone). When operating in the mechanical cooling mode, the controller 78 may monitor operating conditions of the HVAC&R system 10 (e.g., via one or more sensors) to determine the ambient air temperature and / or the temperature of the cooling fluid 58 entering the evaporator 66 (e.g., the chiller inlet liquid temperature, the temperature of the cooling fluid 58 returning from the load 62), such as via feedback received from the return cooling fluid temperature sensor 81. As described above, in some embodiments, based on the ambient air temperature being relatively low (e.g., 1 to 2 Rankine [R] degrees below the temperature of the cooling fluid 58 entering the evaporator 66, 1 to 2R degrees below the temperature of the cooling fluid 58 returned from the load 62, 1 to 2 Fahrenheit [F] degrees below the temperature of the cooling fluid 58 entering the evaporator 66, 1 to 2F degrees below the temperature of the cooling fluid 58 returned from the load 62), the controller 78 may determine that the HVAC&R system 10 may be operated in the hybrid cooling mode to meet the load demand of the HVAC&R system 10. In some embodiments, the controller 78 may determine to transition the operation of the HVAC&R system 10 (at block 202) to the hybrid cooling mode based on the temperature of the cooling fluid 58 entering the evaporator 66 (e.g., the temperature of the cooling fluid 58 returned from the load 62) being lower than the ambient air temperature (e.g., by a threshold amount).

[0064] When operating the HVAC&R system 10 in the hybrid cooling mode, at box 204, the controller 78 may determine the fan speed at which to operate the free cooling system 52 to meet the load demand of the HVAC&R system 10. The controller 78 may determine the appropriate or desired fan speed (e.g., the speed of the fan 60) based on the ambient air temperature and / or the load demand of the HVAC&R system 10. For example, in certain embodiments, the controller 78 may evaluate (e.g., map) the gradient of one or more operating parameters, such as total power, cooling capacity, discharge pressure, motor current, or any combination thereof, with respect to one or more of the compressor speed, the speed of the fan 60 of the air-cooled heat exchanger 56, and / or the speed of the fan 98 of the second air-cooled heat exchanger 97. Additionally, as discussed in more detail below, if no operating constraints are active and / or maintained, the capacity constraint values ​​may be applied to obtain a two-dimensional gradient surface that may be evaluated analytically or by using small increments in each direction on the gradient surface and evaluating the change in total input power.

[0065] In certain embodiments, limits may be established or set (e.g., by the controller 78) for certain operating parameters of the HVAC&R system 10, such as one or more of the discharge pressure, motor current, etc. Each limit may correspond to one of three potential states (an inactive state, a hold state, and an active state). The inactive state may correspond to a state in which the operating parameter does not affect the total input power used by the HVAC&R system 10 to satisfy the load 62. The hold state may correspond to a state in which the operating parameter should be maintained at a current value to mitigate changes in the total input power used by the HVAC&R system 10 to satisfy the load 62. The active state may correspond to a state in which the operation of the HVAC&R system 10 forces movement away from the established limit in a direction defined by a calculated gradient for the corresponding operating parameter. In certain embodiments, if two limits are effective for two corresponding operating parameters, the sum of the two limit gradient vectors may be utilized (e.g., by the controller 78) to determine the direction in which the operating parameter is adjusted to mitigate and / or satisfy the limit. If a single limit is effective for a particular operating parameter, the gradient for the effective limit may be projected onto a surface corresponding to the limit in the hold state. Thus, once the effects of all active and / or maintained constraints for the corresponding operating parameters are considered (e.g., by the controller 78), the capacity constraints may be applied. As described above, if no operating constraints are active and / or maintained for the corresponding operating parameters, applying the capacity constraints may result in a two-dimensional gradient surface. Then, after applying the active and / or maintained constraints, the total power gradient may be projected onto the fixed capacity surface, as described in more detail below.

[0066] In some embodiments, the ambient air temperature may change and / or the cooling load demand of the HVAC&R system 10 may change (e.g., increase). For example, based on the increase in ambient air temperature and / or the increase in the load demand of the HVAC&R system 10, at block 206, the controller 78 may determine that operation in the hybrid cooling mode will not adequately meet the load demand of the HVAC&R system 10. That is, the controller 78 may determine that operating the free cooling system 52 at an upper capacity limit (e.g., the fan 60 associated with the air-cooled heat exchanger 56 operating at an upper speed limit) does not provide sufficient cooling to meet the load demand of the HVAC&R system 10. Therefore, at block 206, the controller 78 may determine to transition operation back to the mechanical cooling mode (e.g., operating the mechanical cooling system 54 alone) to meet the load demand of the HVAC&R system 10, and operation of the free cooling system 52 may be suspended.

[0067] When operating the HVAC&R system 10 in the hybrid cooling mode, the controller 78 may determine that the operation of the free cooling system 52 alone is able to meet the load demand of the HVAC&R system 10. For example, the controller 78 may estimate the free cooling capacity of the free cooling system 52 and may estimate the fan power (e.g., power consumption) of the fan 60 to determine whether the operation of the free cooling system 52 alone results in a low total input power (e.g., lower power consumption of the HVAC&R system 10). Therefore, the controller 78 may continue with the method 200 to evaluate whether the operation of the HVAC&R system 10 should be transitioned from the hybrid cooling mode to the free cooling mode (e.g., operation of the free cooling system 52 alone). To this end, the controller 78 may be configured to estimate and / or determine the power consumption (e.g., total input power) of the HVAC&R system 10 in the hybrid cooling mode and the free cooling mode to evaluate which operating mode is more efficient. For example, at block 208, the controller 78 utilizes various design operating parameters of the HVAC&R system 10 and / or data received from one or more sensors to estimate the condenser effectiveness of the condenser 72 of the HVAC&R system 10 in the hybrid cooling mode. That is, the controller 78 may determine and / or estimate the condenser effectiveness of the condenser 72 based on one or more of the following parameters: operating speed of the fan 60, operating speed of the fan 98, design altitude (e.g., a predetermined value), design ambient air temperature (e.g., a predetermined value), design fan power input (e.g., a predetermined value), design air flow rate (e.g., a predetermined value), design cooling capacity (e.g., a predetermined value), design compressor input power (e.g., a predetermined value), design discharge saturation pressure (e.g., a predetermined value), or any combination thereof to estimate the condenser effectiveness. Further, at block 208, the controller 78 may utilize design operational data (e.g., predetermined values) and / or data received from one or more sensors to calculate an air mass flow rate of ambient air flow directed across the air-cooled heat exchanger 56 (e.g., via the fan 60) and / or the second air-cooled heat exchanger 97 (e.g., via the fan 98). In some embodiments, the condenser effectiveness may vary depending on the air flow rate of ambient air across the air-cooled heat exchanger 56, the second air-cooled heat exchanger 97, the condenser coil 72, and / or the condenser coil 92. In some embodiments, the coefficient may be applied based on the air flow rate of ambient air flow directed across the air-cooled heat exchanger 56 (e.g., the speed of the fan 60) and / or the air flow rate of ambient air flow directed across the second air-cooled heat exchanger 97 (e.g., the speed of the fan 98).

[0068] At block 210, the controller 78 may estimate heat rejection (e.g., heat rejection amount, heat rejection rate) of the condenser 72 of the HVAC&R system 10 based on data received from one or more sensors and / or design performance operating data (e.g., predetermined values). For example, the controller 78 may estimate heat rejection of the condenser 72 of the HVAC&R system 10 using data including one or more of the following: ambient air temperature (e.g., operating ambient air temperature, design ambient air temperature), saturated discharge temperature, saturated suction temperature, temperature of the cooling fluid 58 entering the air-cooled heat exchanger 56, temperature of the cooling fluid 58 leaving the air-cooled heat exchanger 56, temperature of the cooling fluid 58 entering the second air-cooled heat exchanger 97, temperature of the cooling fluid 58 leaving the second air-cooled heat exchanger 97, temperature of the cooling fluid 58 leaving the evaporator 66, design cooling capacity of the free cooling system 52, design cooling capacity of the mechanical cooling system 54, total design cooling capacity of the HVAC&R system 10, design compressor 70 input power, or any combination thereof. It should be noted that when estimating the condenser 72 heat rejection for a particular operating mode of the HVAC&R system 10, the controller 78 may be configured to assume steady-state and / or constant values ​​for one or more calculations performed by the controller 78. In some embodiments, the controller 78 may be configured to monitor operating parameters and assume that the HVAC&R system 10 is operating at a steady state based on operating conditions indicating that certain detected values ​​(e.g., for a particular operating parameter) deviate from each other by less than a threshold amount. For example, the controller 78 may be configured to monitor the input power applied to the HVAC&R system 10, and upon determining that a first input power at a first recorded time deviates from a second input power at a second recorded time by less than a threshold amount (e.g., less than 5%), the controller 78 may assume that the HVAC&R system 10 is operating at a steady state so that the calculations disclosed herein may be performed in a desired manner.

[0069] At block 212, the controller 78 may determine a ratio of cooling capacity provided by each of the cooling systems (e.g., the mechanical cooling system 54, the free cooling system 52) to meet the cooling demand of the HVAC&R system 10 in the hybrid cooling mode. For example, the controller 78 may determine a ratio of cooling capacity provided by the free cooling system 52 to cooling capacity provided by the mechanical cooling system 54 using data received from sensors indicating a temperature of the cooling fluid 58 entering the air-cooled heat exchanger 56, a temperature of the cooling fluid 58 exiting the air-cooled heat exchanger 56, and a flow rate of the cooling fluid 58 exiting the evaporator 66.

[0070] After determining the ratio of the free cooling capacity to the mechanical cooling capacity provided by the HVAC&R system 10 at block 214, the controller 78 may determine the amount of cooling capacity provided by each of the cooling systems (e.g., the free cooling system 52, the mechanical cooling system 54), the total amount of cooling capacity provided by both the free cooling system 52 and the mechanical cooling system 54, employed by the HVAC&R system 10 to meet the load demand of the HVAC&R system 10. The controller 78 may determine the cooling capacity provided by each of the cooling systems employed by the HVAC&R system 10 to meet the load demand based on certain calculations performed in the method 200 discussed above, data from one or more sensors indicative of operating conditions of the HVAC&R system 10, and / or prior data associated with the operation of the HVAC&R system 10 (e.g., historical data, design data). For example, using data received from sensors indicative of saturated discharge temperature, ambient air temperature, and / or compressor 70 input power, the estimated condenser effectiveness determined in block 208, the air mass flow rate of the ambient air flow directed across the air-cooled heat exchanger 56 determined in block 208, the condenser 72 heat rejection determined in block 210, and / or the ratio of free cooling capacity to mechanical cooling capacity determined in block 212, the controller 78 may estimate the cooling capacity provided by the mechanical cooling system 54. Then, using the ratio of free cooling capacity to mechanical cooling capacity, the controller 78 may estimate the amount of cooling capacity provided by the free cooling system 52. The controller 78 may determine the total amount of cooling capacity provided by the HVAC&R system 10 based on the sum of the amount of mechanical cooling capacity and the amount of free cooling capacity.

[0071] When estimating the total amount of cooling capacity provided by the HVAC&R system 10 in the hybrid cooling mode, the controller 78 may determine at block 216 whether the different cooling modes (e.g., operation of the free cooling system 52 alone) are capable of achieving the total cooling capacity determined in block 214. For example, the controller 78 may estimate the total amount of cooling capacity provided by operating the free cooling system 52 at an upper capacity limit (e.g., a fan 60 associated with the air-cooled heat exchanger 56 operating at an upper speed limit) under certain operating conditions (e.g., a particular ambient air temperature). In some embodiments, using design data and / or data received from one or more sensors indicating suction and / or discharge temperature and / or pressure measurements, design fan 60 power, ambient air density at the condenser 72, compressor 70 input power, ambient air temperature, the ratio determined at block 212, and / or other suitable parameters, the controller 78 may determine whether operation in the free cooling mode alone is capable of achieving the total cooling capacity 10 required by the HVAC&R system. In some embodiments, at box 216, the controller 78 may be configured to adjust calculations based on the cooling fluid 58 side resistance (e.g., thermal resistance) and / or the air side resistance (e.g., thermal resistance) when determining whether operation in the free cooling mode alone can meet the load requirements of the HVAC&R system 10.

[0072] Upon determining that operation of the free cooling system 52 alone will not be sufficient to provide the total amount of cooling capacity required by the HVAC&R system 10, the controller 78 may continue to operate the HVAC&R system 10 in the current (e.g., hybrid cooling) operating mode. Upon determining that operation of the free cooling system 52 alone can adequately provide the total amount of cooling capacity required by the HVAC&R system 10, the method 200 may proceed to block 218. At block 218, the controller 78 may determine an estimated input power consumed by the HVAC&R system 10 in the free cooling-only mode to achieve and / or provide the total required cooling capacity.

[0073] In some embodiments, the controller 78 may estimate or determine corresponding amounts of input power (e.g., power consumed by the fan 60), the speed of the fan 60, the ambient air temperature, the ambient air density (e.g., at the condenser 72), and / or the condensing temperature associated with each of the plurality of cooling capacities of the free cooling system 52 at block 218. For example, the controller 78 may iteratively calculate various free cooling capacities provided by the free cooling system 52 and corresponding input powers consumed (e.g., by the fan 60 and / or the fan 98 of the free cooling system 52) to achieve the free cooling capacities based on different fan speeds and / or ambient air temperatures used by the free cooling system 52. As will be appreciated, different fan speeds may be associated with different amounts of input power consumed, and may also be associated with different cooling capacities, based on the ambient air temperature and the air mass flow rate of the ambient air flow directed through the free cooling system 52 (e.g., the ambient air flow directed across the air-cooled heat exchanger 56 via the fan 60, the ambient air flow directed across the second air-cooled heat exchanger 97 via the fan 98, etc.). At block 218, the controller 78 may determine which candidate fan speed(s) may be utilized to achieve the total cooling capacity determined in block 214, and the corresponding input power consumed by operating the free cooling system 52 at a particular fan speed (e.g., the power consumed by the fan 60). That is, the controller 78 may generate one or more input power estimates, and the input power estimates may correspond to different fan speeds that may be capable of meeting the load demand of the HVAC&R system 10.

[0074] At block 220, the controller 78 may compare different input powers associated with different fan speeds (e.g., of the fan 60 and / or the fan 98) that are capable of satisfying the total cooling capacity of the HVAC&R system 10 (e.g., in the free cooling mode) to the total input power consumed by the HVAC&R system 10 in the hybrid cooling mode, which total input power may be derived from one or more sensors. At block 222, the controller 78 may determine to transition from the hybrid cooling mode to the free cooling mode based on the comparison performed in block 220. For example, upon determining that the corresponding total input power associated with the fan speed of the fan 60 that is capable of satisfying the total cooling capacity of the HVAC&R system 10 in the free cooling mode is less than the total input power consumed by the HVAC&R system 10 (e.g., by the fan 60 and the compressor 70) in the hybrid cooling mode, the controller 78 may determine to transition the operation of the HVAC&R system 10 to the free cooling mode. In some embodiments, the controller 78 may be configured to apply a deadband factor before determining whether to transition to the free cooling mode of operation. For example, the controller 78 may apply a deadband (e.g., additional) value, amount, and / or range associated with cooling capacity (e.g., increased cooling capacity, 10 tons), input power consumed, amount of input power over time, percentage of total input power, efficiency metric, and / or other suitable parameters. In this way, the method 200 may enable a reduction in cycling performed by the HVAC&R system 10 (e.g., cycling between different operating modes, on / off cycling of the fan 60 and / or compressor 70), as well as ensure that the load demand of the HVAC&R system 10 will be met via operation in the free cooling mode. For example, in some embodiments, where the controller 78 determines that the free cooling mode is able to provide the total cooling capacity determined in block 214 but is unable to provide the additional 10 tons of cooling capacity (e.g., the deadband value of cooling capacity), the controller 78 may determine that operation of the HVAC&R system 10 should not be transitioned to the free cooling mode.

[0075] When the HVAC&R system is operating in the free cooling mode, at block 224, the controller 78 may determine that the free cooling system 52 cannot meet the load demand (e.g., load 62) of the HVAC&R system 10. For example, based on an increase in ambient air temperature and / or an increase in the load demand 62 of the HVAC&R system 10, the free cooling system 52 may no longer operate to adequately provide the total cooling capacity required by the HVAC&R system 10 when operating the fans 60 and / or fans 98 of the free cooling system 52 (e.g., at an upper capacity). For example, the controller 78 may estimate the HVAC&R system 10 input power at a desired or determined speed of the fans 60 in the hybrid cooling mode, and compare the estimated input power value in the hybrid cooling mode to an input power value associated with operating the fans 60 at an upper capacity in the free cooling mode for a particular (e.g., current) set of operating conditions (e.g., ambient temperature and cooling load). The controller 78 may determine that the estimated input power value in the hybrid cooling mode is less than the input power value corresponding to operating the fans 60 at an upper capacity in the free cooling mode. Therefore, at block 224, the controller 78 may determine to transition back to the hybrid cooling mode, whereby the mechanical cooling system 54 may provide a portion of the total cooling capacity to meet the load demand of the HVAC&R system 10. In some embodiments, the transition from the free cooling mode to the hybrid cooling mode and / or the transition from the hybrid cooling mode to the mechanical cooling mode may be based on a determination that the temperature difference between the temperature of the cooling fluid 58 entering the air-cooled heat exchanger 56 and the ambient air temperature falls below a threshold difference.

[0076] In certain embodiments, the visual model can facilitate understanding of the above-described optimization process that enables transitions between various available cooling modes. For example, the total input power of the HVAC&R system 10 can be represented by a surface. The slope of the surface can correspond to the gradient of the total input power. The gradient can be a vector pointing in the direction of the steepest slope of the surface. A positive gradient value can indicate that the total input power increases as the speed of the fan 60 increases, and thus a lower speed associated with the fan 60 corresponds to a higher relative efficiency. Similarly, a negative gradient can indicate that a higher speed of the fan 60 can result in greater efficiency. In embodiments where there are no active constraints, improved or desired efficiency can occur at zero gradient. Therefore, for a given surface representing the total input power of the HVAC&R system 10, a gradient can be evaluated, thereby achieving an incremental adjustment of the fan speed to reduce total energy use (e.g., reduce power consumption). In some embodiments, the output of the evaluation can correspond to a new discharge pressure set point (e.g., an adjustment in the operation of the compressor 70) and / or a direct change in the speed of the fan 60.

[0077] In embodiments where active constraints exist, fan speed may be limited by discharge pressure or oil pressure, and the fan speed of one system (e.g., vapor compression system, free cooling system) may have an effect on the discharge pressure of another system (e.g., vapor compression system). For example, in embodiments where a first system (e.g., vapor compression system) has an active discharge pressure limit and a second system (e.g., vapor compression system) does not have an active discharge pressure limit, increasing the fan speed for the second system will increase the free cooling capacity, which can reduce the capacity required from the corresponding compressors of the two systems. Even without changing the fan speed for the system, a lower relative compressor capacity can reduce the discharge pressure for the first system. Existing controls may not take into account this interaction, but may rely on feedback indicating the temperature of the cooling fluid 58 leaving the evaporator 66 and / or the discharge pressure of the cooling fluid 58 leaving the evaporator 66. For example, an estimated desired fan speed for the fan 60 can be calculated, and a pressure limit can override the implementation of the fan speed. Therefore, using the above example, increasing the fan speed for the second system will increase the cooling capacity. After a delay (e.g., 1 second, 2 seconds, 5 seconds, or longer), the cooler cooling fluid from the free cooling heat exchanger will result in a lower temperature of the liquid leaving the evaporator. The HVAC&R system 10 capacity control may respond by reducing the compressor speed, resulting in a lower discharge pressure for both systems. The controller may then reduce the fan speed for the first system to restore the discharge pressure to an acceptable value. Thus, an increase in fan speed for one system may force a decrease in fan speed for another system, and if this interaction is ignored, the estimated final operating point may deviate from the desired operating condition. Additionally, the time delays involved in the interaction may create or amplify stability issues.

[0078] To address the shortcomings discussed above, the interaction between the gradient G and the constraint can be described using the following equation (1). The constraint is represented as a surface with a unit normal vector n, and θ is the angle between G and n. The vector P is the gradient G projected onto the constraint surface and is determined using the following equation (1).

[0079] P=Gn(n·G) (1)

[0080] Equation 1 may be valid for the case where n·G is positive. A negative value for this dot product indicates that the gradient is moving away from the constraint and therefore the constraint is no longer valid. In certain embodiments, additional equations may be utilized in accordance with the present technique. For example, using the VSD 71 frequency of the compressor 70 (i.e., Hz 压缩机 ), the discharge pressure of the working fluid 76 (ie, P 排放，极限 ) limit value, the suction pressure of the working fluid 76 (ie, P 吸入 ), the average air pressure at a given altitude (i.e., P平均，高度 ), the saturated suction temperature (ie, STP) of the working fluid 76 in the evaporator 66, and the liquid temperature (T 液体 ) (e.g., the temperature of the working fluid 76 leaving the condenser 72), equation (2) may be used to estimate the cooling capacity of a particular embodiment of the HVAC&R system 10 (i.e., TR 蒸发器，估计 ).

[0081]

[0082] In certain embodiments, C TR , C 0,Hz , C 1,Hz Each of the values ​​may be a constant derived based on an operating parameter of the cooling fluid 58 directed through the HVAC&R system 10. Additionally, the constant C TR , C 0,Hz , C 1,Hz may depend on other operating parameters associated with the working fluid 76 directed through the HVAC&R system 10. For example, C 0,TR The value can be determined using the following equation (3), where B 0,TR , B 1,TR and B 2,TR is a constant derived based on the particular working fluid 76 being directed through HVAC&R system 10 .

[0083] C 0，TR ≡B 0，TR +B 1，TR STP+B 2，TR STP 2 (3)

[0084] Similarly, C 1,TR The value can be determined using the following equation (4), where M 0,TR 、M 1,TR 、M 2,TR and M 3,TR φ is also a constant derived based upon the particular working fluid 76 being directed through the HVAC&R system 10 .

[0085] C 1，TR ≡M 0，TR +M 1，TR ·STP+M 2，TR STP 2 +M 3，TR STP 3 (4)

[0086] In some embodiments, the average air pressure at a given altitude (i.e., P 平均，高度) can be determined based on the installation height of the HVAC&R system 10 (ie, Alt) using the following equation (5).

[0087] p 平均，高度 =14.696·[1-(6.8754E-6)·Alt] 5.2559 (5)

[0088] Additionally, in some embodiments, the COP 压缩机，极限 ) An estimate of the coefficient of performance of the compressor 70 associated with the compressor 70 can be calculated using the following equation (6), where B COP and M COP is a constant derived based on cooling fluid 58 directed through HVAC&R system 10 .

[0089]

[0090] In addition, the following equation (7) can be used to use the coefficient of performance (i.e., COP) determined by the above equation (6) 压缩机，极限 ) and the cooling capacity of the HVAC&R system 10 (i.e., TR 蒸发器，估计 ) to calculate the specific discharge pressure limit value (ie, THR) of the working fluid 76 极限 ) is an estimate of the total heat rejection from the coils of the condenser 72.

[0091] THR 极限 =TR 蒸发器，估计 ·(1+COP 压缩机，极限 ) (7)

[0092] In certain embodiments, the following equation (8) may be used to calculate the limit value based on the discharge pressure (ie, P 排放，极限 ) and a constant value C derived based on the working fluid 76 directed through the HVAC&R system 10 0，P排放 , C 1，P排放 and C 2，P排放 To calculate the working fluid 76 at a specific discharge pressure limit (ie, DTP 极限 ) is an estimate of the saturated discharge temperature under .

[0093]

[0094] Furthermore, based on the values ​​derived from the above equations, the following equation (9) can be used to determine the fan 60 at a specific discharge pressure limit value (ie, Hz): 风扇，极限 ) under the estimated speed, where C 0,UA and C 1,UA is a constant derived based on the frequency applied to the fan 60 of the HVAC&R system 10, and T环境 is a temperature value associated with the ambient air surrounding the HVAC&R system 10. For example, at a particular discharge pressure limit (i.e., DTP 极限 The estimated value of the saturated discharge temperature at ) can be obtained from the above equation (8) and at a specific discharge pressure limit value (ie, THR 极限 ) can be obtained from equation (7) above. Therefore, using the above values, equation (9) can be used to determine the total heat rejection across the coil of condenser 72 at a specific discharge pressure limit (i.e., Hz 风扇，极限 )The estimated speed of the fan 60.

[0095]

[0096] The present disclosure may provide one or more technical effects useful in the operation of an HVAC&R system. For example, an HVAC&R system may include a mechanical cooling system and a free cooling system, and may therefore be able to operate in various cooling modes (e.g., only mechanical cooling mode, only free cooling mode, mixed cooling mode) to meet the load requirements of the HVAC&R system while increasing efficiency. The HVAC&R system may utilize various methods to control the operation of the HVAC&R system, including methods to control transitions between available cooling modes to meet the cooling load while limiting the amount of energy consumed by the HVAC&R system. By monitoring the operating conditions of the HVAC&R system (e.g., via one or more sensors) and / or utilizing design and / or historical data, the total amount of cooling capacity provided by the cooling mode under which the HVAC&R system is operating may be determined by a controller. The controller may also determine whether different cooling modes are able to meet the total cooling capacity provided by the current cooling mode of the HVAC&R system. If different cooling modes are able to provide the total cooling capacity required by the HVAC&R system, the corresponding total input power for the different cooling modes may be determined, thereby enabling a comparison of the total input power for the current cooling mode of the HVAC&R system and the different cooling modes. In this way, the controller can select a cooling mode with reduced total input power but still able to meet the load demand of the HVAC&R system. Therefore, the technology discussed herein enables the HVAC&R system to operate more efficiently at a reduced cost (e.g., reduced energy input). The technical effects and technical problems in the specification are examples and are not limiting. It should be noted that the embodiments described in the specification may have other effects and may solve other technical problems.

[0097] Although only certain features and embodiments are shown and described, many modifications and changes may occur to those skilled in the art without materially departing from the novel teachings and advantages of the subject matter recited in the claims, such as changes in size, dimensions, structure, shape and proportion of various elements, parameter values ​​(such as temperature and pressure), mounting arrangements, use of materials, color, orientation, etc. The order or sequence of any process or method steps may be changed or re-sequenced according to alternative embodiments. Therefore, it should be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the present disclosure.

[0098] Furthermore, in an effort to provide a concise description of exemplary embodiments, not all features of an actual implementation may be described, such as those not relevant to the best mode currently contemplated or those not relevant to enablement. It should be appreciated that in the development of such actual implementations, as in any engineering or design project, numerous implementation-specific decisions may be made. Such development work may be complex and time consuming, but these are routine tasks of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure, without undue experimentation.

[0099] The techniques presented and claimed herein refer to and apply to substantial objects and specific examples of a practical nature that improve the technical field of the invention in a demonstrable manner and are therefore not abstract, intangible, or purely theoretical. In addition, if any claim appended to the end of this specification contains one or more elements expressed as "means for [performing] [the function] ..." or "steps for [performing] [the function] ...", it is expected that such elements will be interpreted in accordance with 35 U.S.C. 112(f). However, for any claim containing elements specified in any other manner, it is intended that such elements will not be interpreted in accordance with 35 U.S.C. 112(f).

Claims

1. A heating, ventilation, air conditioning, and refrigeration (HVAC&R) system configured to operate in multiple cooling modes, comprising: a mechanical cooling system configured to place the working fluid in heat exchange relationship with a cooling fluid; a free cooling system configured to place the cooling fluid in a second heat exchange relationship with an ambient air flow; and A controller comprising processing circuitry and memory, wherein the memory comprises instructions that, when executed by the processing circuitry, are configured to cause the processing circuitry to transition operation of the HVAC&R system between the plurality of cooling modes based on a cooling demand of the HVAC&R system and based on an estimated power consumption of the HVAC&R system.

2. The HVAC&R system of claim 1 , wherein the instructions, when executed by the processing circuitry, are configured to cause the processing circuitry to: operating the mechanical cooling system in a mechanical cooling mode among the plurality of cooling modes and suspending operation of the free cooling system; operating the free cooling system in a free cooling mode of the plurality of cooling modes and suspending operation of the mechanical cooling system; and The mechanical cooling system is operated in a mixed cooling mode among the plurality of cooling modes and the free cooling system is operated.

3. The HVAC&R system of claim 2, wherein the instructions, when executed by the processing circuit system, are configured to cause the processing circuit system to transition operation of the HVAC&R system from the mechanical cooling mode to the hybrid cooling mode based on a determination that the ambient air temperature is less than the temperature of the cooling fluid received by the HVAC&R system.

4. The HVAC&R system of claim 2, wherein the instructions, when executed by the processing circuitry, are configured to cause the processing circuitry to: The operation of the HVAC&R system is transitioned from the hybrid cooling mode to the free cooling mode based on a first determination that operation of the HVAC&R system in the free cooling mode is expected to meet the cooling demand and based on a second determination that a first estimated power consumption of the HVAC&R system in the free cooling mode is less than a second estimated power consumption of the HVAC&R system in the hybrid cooling mode.

5. The HVAC&R system of claim 4, wherein the free cooling system includes a heat exchanger configured to direct the cooling fluid therethrough and a fan configured to force the ambient air flow across the heat exchanger, and wherein the instructions, when executed by the processing circuit system, are configured to cause the processing circuit system to estimate the power consumption of the fan to determine the first estimated power consumption, the second estimated power consumption, or both.

6. The HVAC&R system of claim 5, wherein the mechanical cooling system includes a compressor configured to direct the working fluid through the mechanical cooling system, and wherein the instructions, when executed by the processing circuit system, are configured to cause the processing circuit system to estimate a power consumption of the compressor to determine the second estimated power consumption.

7. The HVAC&R system of claim 6, wherein the mechanical cooling system includes a condenser configured to place the working fluid in a third heat exchange relationship with the ambient air flow, and wherein the instructions, when executed by the processing circuit system, are configured to cause the processing circuit system to estimate the effectiveness of the condenser to determine the second estimated power consumption.

8. The HVAC&R system of claim 4, wherein the instructions, when executed by the processing circuitry, are configured to cause the processing circuitry to: The HVAC&R system is transitioned from the free cooling mode to the hybrid cooling mode based on a third determination that the second estimated power consumption of the HVAC&R system in the hybrid cooling mode is less than the first estimated power consumption of the HVAC&R system in the free cooling mode.

9. The HVAC&R system of claim 4, wherein the instructions, when executed by the processing circuitry, are configured to cause the processing circuitry to: Operation of the HVAC&R system is transitioned from the free cooling mode to the hybrid cooling mode based on a third determination that operation of the HVAC&R system in the free cooling mode is not expected to meet the cooling demand.

10. A tangible, non-transitory computer-readable medium comprising instructions executable by processing circuitry of a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system, the instructions, when executed by the processing circuitry, causing the processing circuitry to: operating a mechanical cooling system and a free cooling system in a hybrid cooling mode of the HVAC&R system; calculating an estimated total amount of cooling capacity provided by the HVAC&R system in the hybrid cooling mode; calculating a first estimated amount of input power consumed by the mechanical cooling system and the free cooling system in the hybrid cooling mode to provide the estimated total amount of cooling capacity; determining the estimated total amount of cooling capacity that operation of the free cooling system and suspended operation of the mechanical cooling system are expected to provide in a free cooling mode of the HVAC&R system; calculating a second estimated amount of input power consumed by the free cooling system in the free cooling mode to provide the estimated total amount of cooling capacity; comparing the first estimate of input power to the second estimate of input power; as well as Operation of the HVAC&R system is transitioned from the hybrid cooling mode to the free cooling mode in response to a determination that the second estimate of input power is less than the first estimate of input power.

11. The computer-readable medium of claim 10, wherein the instructions, when executed by the processing circuitry, cause the processing circuitry to: calculating the effectiveness of a condenser of the mechanical cooling system based on an operating speed of a fan of the mechanical cooling system, an ambient air temperature, an estimated mass flow rate of ambient air directed through the condenser, a first power input of the fan, a second power input of a compressor of the mechanical cooling system, or a combination thereof; and The estimated total amount of cooling capacity is calculated based on the effectiveness of the condenser.

12. The computer-readable medium of claim 10, wherein the instructions, when executed by the processing circuitry, cause the processing circuitry to calculate an estimated input power for a fan of the free cooling system based on the second estimate of input power consumed by the free cooling system in the free cooling mode.

13. The computer-readable medium of claim 10, wherein the instructions, when executed by the processing circuitry, cause the processing circuitry to determine a ratio of a first amount of the estimated total amount of cooling capacity provided by the mechanical cooling system to a second amount of the estimated total amount of cooling capacity provided by the free cooling system.

14. The computer-readable medium of claim 10, wherein the instructions, when executed by the processing circuitry, cause the processing circuitry to transition operation of the HVAC&R system from the free cooling mode to the hybrid cooling mode in response to an additional determination that the first estimate of input power is less than the second estimate of input power.

15. The computer-readable medium of claim 10, wherein the instructions, when executed by the processing circuitry, cause the processing circuitry to operate the mechanical cooling system in a mechanical cooling mode of the HVAC&R system and suspend operation of the free cooling system based on an additional determination that the ambient air temperature is greater than the temperature of the cooling fluid received by the HVAC&R system.

16. The computer-readable medium of claim 10, wherein the instructions, when executed by the processing circuitry, cause the processing circuitry to adjust operation of a compressor of the mechanical cooling system and to adjust operation of a fan of the free cooling system in the hybrid cooling mode to reduce power consumption of the HVAC&R system.

17. The computer-readable medium of claim 10, wherein the instructions, when executed by the processing circuit system, cause the processing circuit system to transition operation of the HVAC&R system from the hybrid cooling mode to the free cooling mode in response to an additional determination that operation of the HVAC&R system in the free cooling mode is expected to provide greater than the estimated total amount of cooling capacity.

18. A heating, ventilation, air conditioning and refrigeration (HVAC&R) system comprising: a mechanical cooling system configured to circulate a working fluid therethrough and to transfer heat from the cooling fluid to the working fluid; a free cooling system configured to circulate the cooling fluid therethrough and transfer heat from the cooling fluid to ambient air; and A controller, the controller being configured to: operating the mechanical cooling system in a mechanical cooling mode of the HVAC&R system and suspending operation of the free cooling system; operating the free cooling system in a free cooling mode of the HVAC&R system and suspending operation of the mechanical cooling system; operating the mechanical cooling system and operating the free cooling system in a hybrid cooling mode of the HVAC&R system; as well as Operation of the HVAC&R system is transitioned between the mechanical cooling mode, the free cooling mode, and the hybrid cooling mode based on a cooling demand of the HVAC&R system, a first power consumption associated with operation of the mechanical cooling system, and a second power consumption associated with operation of the free cooling system.

19. The HVAC&R system of claim 18, wherein the controller is configured to: transitioning operation of the HVAC&R system from the mechanical cooling mode to the hybrid cooling mode based on a first determination that an ambient air temperature is less than a temperature of the cooling fluid received by the HVAC&R system; and The operation of the HVAC&R system is transitioned from the hybrid cooling mode to the free cooling mode based on a second determination that operation of the HVAC&R system in the free cooling mode is expected to provide a first cooling capacity in the free cooling mode that is equal to or greater than a second cooling capacity of the HVAC&R system in the hybrid cooling mode, and based on a third determination that a first estimated power consumption of the HVAC&R system in the free cooling mode is less than a second estimated power consumption of the HVAC&R system in the hybrid cooling mode.

20. The HVAC&R system of claim 19, wherein the first estimated power consumption includes a power input to a fan of the free cooling system, and the second estimated power consumption includes a power input to a compressor of the mechanical cooling system and a power input to the fan of the free cooling system.

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